Hydrogen Sulfide-Activatable Second Near-Infrared Fluorescent Nanoassemblies for Targeted Photothermal Cancer Therapy

High-Performance NIR-II Fluorescent Type I/II Photosensitizer Enabling Augmented Mild Photothermal Therapy of Tumors by Disrupting Heat Shock Proteins

NIR-II fluorescent photosensitizers as phototheranostic agents hold considerable promise in the application of mild photothermal therapy (MPTT) for tumors, as the reactive oxygen species generated during photodynamic therapy can effectively disrupt heat shock proteins. Nevertheless, the exclusive utilization of these photosensitizers to significantly augment the MPTT efficacy has rarely been substantiated, primarily due to their insufficient photodynamic performance. Herein, the utilization of high-performance NIR-II fluorescent type I/II photosensitizer (AS21:4) is presented as a simple but effective nanoplatform derived from molecule AS2 to enhance the MPTT efficacy of tumors without any additional therapeutic components. By taking advantage of heavy atom effect, AS21:4 as a type I/II photosensitizer demonstrates superior efficacy in producing 1O2 (1O2 quantum yield = 12.4%) and O2 •- among currently available NIR-II fluorescent photosensitizers with absorption exceeding 800 nm. In vitro and in vivo findings demonstrate that the 1O2 and O2 •- generated from AS21:4 induce a substantial reduction in the expression of HSP90, thereby improving the MPTT efficacy. The remarkable phototheranostic performance, substantial tumor accumulation, and prolonged tumor retention of AS21:4, establish it as a simple but superior phototheranostic agent for NIR-II fluorescence imaging-guided MPTT of tumors.

An Intramolecular Rotor-Bridged Dimeric Cyanine Photothermal Transducer for Efficient Near-Infrared II Fluorescence Imaging-Guided Mitochondria-Targeted Phototherapy

Near-infrared (NIR) heptamethine cyanine (HCy) dyes are promising photothermal transducers for image-guided cancer treatment owing to their prominent photophysical properties and high photothermal conversion ability. However, HCy photothermal transducers usually have poor photostability due to degradation induced by the self-generated reactive oxygen species. Herein, a novel mitochondria-targeting dimeric HCy dye, named dimeric oBHCy, is rationally designed, exhibiting strong near-infrared II (NIR-II) fluorescence emission, high photothermal conversion efficiency (PCE), and excellent photostability. The large π-conjugation and drastic intramolecular motion of the diphenol rotor in the dimeric oBHCy enhance the nonradiative energy dissipation and suppress the intersystem crossing process, thereby achieving a high PCE (49.2%) and improved photostability. Impressively, dimeric oBHCy can precisely target mitochondria and induce mitochondrial damage upon NIR light irradiation. Under the guidance of in vivo NIR-II fluorescence imaging, efficient NIR light-activated photothermal therapy of 4T1 breast tumors is accomplished with a tumor inhibitory rate of 96% following a single injection of the dimeric oBHCy. This work offers an innovative strategy for designing cyanine photothermal transducers with integrated NIR-II fluorescence and photothermal properties for efficient cancer theranostics.

Aggregation-enhanced photothermal therapy of organic dyes

Photothermal therapy (PTT) represents a groundbreaking approach to targeted disease treatment by harnessing the conversion of light into heat. The efficacy of PTT heavily relies on the capabilities of photothermal agents (PTAs). Among PTAs, those based on organic dyes exhibit notable characteristics such as adjustable light absorption wavelengths, high extinction coefficients, and high compatibility in biological systems. However, a challenge associated with organic dye-based PTAs lies in their efficiency in converting light into heat while maintaining stability. Manipulating dye aggregation is a key aspect in modulating non-radiative decay pathways, aiming to augment heat generation. This review delves into various strategies aimed at improving photothermal performance through constructing aggregation. These strategies including protecting dyes from photodegradation, inhibiting non-photothermal pathways, maintaining space within molecular aggregates, and introducing intermolecular photophysical processes. Overall, this review highlights the precision-driven assembly of organic dyes as a promising frontier in enhancing PTT-related applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Theranostic Fluorescent Probes

The ability to gain spatiotemporal information, and in some cases achieve spatiotemporal control, in the context of drug delivery makes theranostic fluorescent probes an attractive and intensely investigated research topic. This interest is reflected in the steep rise in publications on the topic that have appeared over the past decade. Theranostic fluorescent probes, in their various incarnations, generally comprise a fluorophore linked to a masked drug, in which the drug is released as the result of certain stimuli, with both intrinsic and extrinsic stimuli being reported. This release is then signaled by the emergence of a fluorescent signal. Importantly, the use of appropriate fluorophores has enabled not only this emerging fluorescence as a spatiotemporal marker for drug delivery but also has provided modalities useful in photodynamic, photothermal, and sonodynamic therapeutic applications. In this review we highlight recent work on theranostic fluorescent probes with a particular focus on probes that are activated in tumor microenvironments. We also summarize efforts to develop probes for other applications, such as neurodegenerative diseases and antibacterials. This review celebrates the diversity of designs reported to date, from discrete small-molecule systems to nanomaterials. Our aim is to provide insights into the potential clinical impact of this still-emerging research direction.

Dual-Responsive Near-Infrared BODIPY-Based Fluorescent Probe for the Detection of F- and HClO in Organisms

Fluoride anions (F-) play a crucial role in human physiological processes. However, excessive intake of F- would affect oxygen metabolism and promote the generation of oxygen-free radicals. Hence, it is essential to develop a precise and efficient fluorescent probe for visualizing F--induced oxidative stress. In this work, we developed the first bifunctional BODIPY-based fluorescent probe dfBDP with p-tert-butyldimethylsilanolate benzyl thioether as the sensing site for the detection of F- and HClO via two distinct reactions, the self-immolative removal and the thioether oxidation, which generate the sensing products with two nonoverlap fluorescence bands: 800-1200 and 500-750 nm, respectively. The probe dfBDP displays rapid response, high specificity, and sensitivity for the detection of F- (LOD, 316.2 nM) and HClO (LOD, 33.9 nM) in vitro. Cellular imaging reveals a correlation between F--induced oxidative stress and the upregulation of HClO. Finally, probe dfBDP was employed to detect F- and HClO in mice under the stimulation of F-. The experimental results display that the level of HClO elevates in the liver of mice.

Recent Progress on Tumor Microenvironment-Activated NIR-II Phototheranostic Agents with Simultaneous Activation for Diagnosis and Treatment

Malignant tumors seriously threaten human life and well-being. Emerging Near-infrared II (NIR-II, 1000-1700 nm) phototheranostic nanotechnology integrates diagnostic and treatment modalities, offering merits including improved tissue penetration and enhanced spatiotemporal resolution. This remarkable progress has opened promising avenues for advancing tumor theranostic research. The tumor microenvironment (TME) differs from normal tissues, exhibiting distinct attributes such as hypoxia, acidosis, overexpressed hydrogen peroxide, excess glutathione, and other factors. Capitalizing on these attributes, researchers have developed TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic attributes concurrently. Therefore, developing TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic activation holds significant research importance. Currently, research on TME-activatable NIR-II phototheranostic agents is still in its preliminary stages. This review examines the recent advances in developing dual-functional NIR-II activatable phototheranostic agents over the past years. It systematically presents NIR-II phototheranostic agents activated by various TME factors such as acidity (pH), hydrogen peroxide (H2 O2 ), glutathione (GSH), hydrogen sulfide (H2 S), enzymes, and their hybrid. This encompasses NIR-II fluorescence and photoacoustic imaging diagnostics, along with therapeutic modalities, including photothermal, photodynamic, chemodynamic, and gas therapies triggered by these TME factors. Lastly, the difficulties and opportunities confronting NIR-II activatable phototheranostic agents in the simultaneous diagnosis and treatment field are highlighted.

Hydrogen sulfide responsive nanoplatforms: Novel gas responsive drug delivery carriers for biomedical applications

Hydrogen sulfide (H2S) is a toxic, essential gas used in various biological and physical processes and has been the subject of many targeted studies on its role as a new gas transmitter. These studies have mainly focused on the production and pharmacological side effects caused by H2S. Therefore, effective strategies to remove H2S has become a key research topic. Furthermore, the development of novel nanoplatforms has provided new tools for the targeted removal of H2S. This paper was performed to review the association between H2S and disease, related H2S inhibitory drugs, as well as H2S responsive nanoplatforms (HRNs). This review first analyzed the role of H2S in multiple tissues and conditions. Second, common drugs used to eliminate H2S, as well as their potential for combination with anticancer agents, were summarized. Not only the existing studies on HRNs, but also the inhibition H2S combined with different therapeutic methods were both sorted out in this review. Furthermore, this review provided in-depth analysis of the potential of HRNs about treatment or detection in detail. Finally, potential challenges of HRNs were proposed. This study demonstrates the excellent potential of HRNs for biomedical applications.

Tumor microenvironment-activated theranostic nanoreactor for NIR-II Photoacoustic imaging-guided tumor-specific photothermal therapy

Theranostic agents that can be sensitively and specifically activated by the tumor microenvironment (TME) have recently attracted considerable attention. In this study, TME-activatable 3,3',5,5'-tetramethylbenzidine (TMB)-copper peroxide (CuO2)@poly(lactic-co-glycolic acid) (PLGA)@red blood cell membrane (RBCM) (TCPR) nanoparticles (NPs) for second near-infrared photoacoustic imaging-guided tumor-specific photothermal therapy were developed by co-loading CuO2 NPs and TMB into PLGA camouflaged by RBCMs. As an efficient H2O2 supplier, once exposed to a proton-rich TME, CuO2 NPs can generate H2O2 and Cu2+, which are further reduced to Cu+ by endogenous glutathione. Subsequently, the Cu+-mediated Fenton-like reaction produces cytotoxic ·OH to kill the cancer cells and induce TMB-mediated photoacoustic and photothermal effects. Combined with the RBCM modification-prolonged blood circulation, TCPR NPs display excellent specificity and efficiency in suppressing tumor growth, paving the way for more accurate, safe, and efficient cancer theranostics.

Trisulfide Bond-Mediated Molecular Phototheranostic Platform for "Activatable" NIR-II Imaging-Guided Enhanced Gas/Chemo-Hypothermal Photothermal Therapy

Tumor microenvironment (TME)-triggered phototheranostic platform offers a feasible strategy to improve cancer diagnosis accuracy and minimize treatment side effects. Developing a stable and biocompatible molecular phototheranostic platform for TME-activated second near-infrared (NIR-II) fluorescence imaging-guided multimodal cascade therapy is a promising strategy for creating desirable anticancer agents. Herein, a new NIR-II fluorescence imaging-guided activatable molecular phototheranostic platform (IR-FEP-RGD-S-S-S-Fc) is presented for actively targeted tumor imaging and hydrogen sulfide (H2 S) gas-enhanced chemodynamic-hypothermal photothermal combined therapy (CDT/HPTT). It is revealed for the first time that the coupling distance between IR-FE and ferrocene is proportional to the photoinduced electron transfer (PET), and the aqueous environment is favorable for PET generation. The part of Cyclic-RGDfK (cRGDfk) peptides can target the tumor and benefit the endocytosis of nanoparticles. The high-concentration glutathione (GSH) in the TME will separate the fluorescence molecule and ferrocene by the GSH-sensitive trisulfide bond, realizing light-up NIR-II fluorescence imaging and a cascade of trimodal synergistic CDT/HPTT/gas therapy (GT). In addition, the accumulation of hydroxyl radicals (•OH) and down-regulation of glutathione peroxidase 4 (GPX4) can produce excessive harmful lipid hydroperoxides, ultimately leading to ferroptosis.

Tumor Microenvironment-Responsive One-for-All Molecular-Engineered Nanoplatform Enables NIR-II Fluorescence Imaging-Guided Combinational Cancer Therapy

The activable NIR-based phototheranostic nanoplatform (NP) is considered an efficient and reliable tumor treatment due to its strong targeting ability, flexible controllability, minimal side effects, and ideal therapeutic effect. This work describes the rational design of a second near-infrared (NIR-II) fluorescence imaging-guided organic phototheranostic NP (FTEP-TBFc NP). The molecular-engineered phototheranostic NP has a sensitive response to glutathione (GSH), generating hydrogen sulfide (H2S) gas, and delivering ferrocene molecules in the tumor microenvironment (TME). Under 808 nm irradiation, FTEP-TBFc could not only simultaneously generate fluorescence, heat, and singlet oxygen but also greatly enhance the generation of reactive oxygen species to improve chemodynamic therapy (CDT) and photodynamic therapy (PDT) at a biosafe laser power of 0.33 W/cm2. H2S inhibits the activity of catalase and cytochrome c oxidase (COX IV) to cause the enhancement of CDT and hypothermal photothermal therapy (HPTT). Moreover, the decreased intracellular GSH concentration further increases CDT's efficacy and downregulates glutathione peroxidase 4 (GPX4) for the accumulation of lipid hydroperoxides, thus causing the ferroptosis process. Collectively, FTEP-TBFc NPs show great potential as a versatile and efficient NP for specific tumor imaging-guided multimodal cancer therapy. This unique strategy provides new perspectives and methods for designing and applying activable biomedical phototheranostics.

Specific imaging of intracellular hydrogen sulfide by a positively charged NIR fluorescent probe

The poor water solubility of traditional activatable organic molecular probes usually limits their detection ability in physiological environment. In this work, a positively charged H2S probe was designed, which exhibited a significantly enhanced responsiveness to H2S in the aggregated state due to the increased positive charge density on the aggregate surface. Under physiological conditions, the probe could be activated by H2S with specificity and sensitivity to release near-infrared fluorescence signal. Moreover, endogenous H2S levels in living cells were successfully monitored by using this probe. We expect that this probe can provide a new strategy for the design of activatable probes to break the limitation of poor water solubility of conventional organic molecular probes.

Near-Infrared-II Fluorophore with Inverted Dependence of Fluorescence Quantum Yield on Polarity as Potent Phototheranostics for Fluorescence-Image-Guided Phototherapy of Tumors

Organic phototheranostics simultaneously having fluorescence in the second near-infrared (NIR-II, 1000-1700 nm) window, and photothermal and photodynamic functions possess great prospects in tumor diagnosis and therapy. However, such phototheranostics generally suffer from low brightness and poor photodynamic performance due to severe solvatochromism. Herein, an organic NIR-II fluorophore AS1, which possesses an inverted dependence of fluorescence quantum yield on polarity, is reported to serve as potent phototheranostics for tumor diagnosis and therapy. After encapsulation of AS1 into nanostructures, the obtained phototheranostics (AS1R ) exhibit high extinction coefficients (e.g., 68200 L mol-1  cm-1 at 808 nm), NIR-II emission with high fluorescence quantum yield up to 4.7% beyond 1000 nm, photothermal conversion efficiency of ≈65%, and 1 O2 quantum yield up to 4.1%. The characterization of photophysical properties demonstrates that AS1R is superior to other types of organic phototheranostics in brightness, photothermal effect, and photodynamic performance at the same mass concentration. The excellent phototheranostic performance of AS1R enables clear visualization and complete elimination of tumors using a single and low injection dose. This study demonstrates the merits and prospects of NIR-II fluorophore with inverted polarity dependence of fluorescence quantum yield as high-performance phototheranostic agents for fluorescence imaging and phototherapy of tumors.

Activatable probes with potential for intraoperative tumor-specific fluorescence-imaging guided surgery

Owing to societal development and aging population, the impact of cancer on human health and quality of life has increased. Early detection and surgical treatment are the most effective approaches for most cancer patients. As the scope of conventional tumor resection is determined by auxiliary examination and surgeon experience, there is often insufficient recognition of tiny tumors. The ability to detect such tumors can be improved by using fluorescent tumor-specific probes for surgical navigation. This review mainly describes the design principles and mechanisms of activatable probes for the fluorescence imaging of tumors. This type of probe is nonfluorescent in normal tissue but exhibits obvious fluorescence emission upon encountering tumor-specific substrates, such as enzymes or bioactive molecules, or changes in the microenvironment, such as a low pH. In some cases, a single-factor response does not guarantee the effective fluorescence labeling of tumors. Therefore, two-factor-activatable fluorescence imaging probes that react with two specific factors in tumor cells have also been developed. Compared with single biomarker testing, the simultaneous monitoring of multiple biomarkers may provide additional insight into the role of these substances in cancer development and aid in improving the accuracy of early cancer diagnosis. Research and progress in this field can provide new methods for precision medicine and targeted therapy. The development of new approaches for early diagnosis and treatment can effectively improve the prognosis of cancer patients and help enhance their quality of life.

A Supramolecular Naphthalene Diimide Radical Anion with Efficient NIR-II Photothermal Conversion for E. coli-Responsive Photothermal Therapy

We report a supramolecular naphthalene diimide (NDI) radical anion with efficient NIR-II photothermal conversion for E. coli-responsive photothermal therapy. The supramolecular radical anion (NDI-2CB[7])⋅- , which is obtained from the E. coli-induced in situ reduction of NDI-2CB[7] neutral complex, formed by the host-guest interaction between an NDI derivative and cucurbit[7]uril (CB[7]), exhibits unexpectedly strong NIR-II absorption and remarkable photothermal conversion capacity in aqueous solution. The NIR-II absorption is caused by the self-assembly of NDI radical anions to form supramolecular dimer radicals in aqueous solution, which is supported by theoretically predicted spectra. The (NDI-2CB[7])⋅- demonstrates excellent NIR-II photothermal antimicrobial activity (>99 %). This work provides a new approach for constructing NIR-II photothermal agents and non-contact treatments for bacterial infections.

Recent advances in fluorescence imaging-guided photothermal therapy and photodynamic therapy for cancer: From near-infrared-I to near-infrared-II

Phototherapy (including photothermal therapy, PTT; and photodynamic therapy, PDT) has been widely used for cancer treatment, but conventional PTT/PDT show limited therapeutic effects due to the lack of disease recognition ability. The integration of fluorescence imaging with PTT/PDT can reveal tumor locations in a real-time manner, holding great potential in early diagnosis and precision treatment of cancers. However, the traditional fluorescence imaging in the visible and near-infrared-I regions (VIS/NIR-I, 400-900 nm) might be interfered by the scattering and autofluorescence from tissues, leading to a low imaging resolution and high false positive rate. The deeper near-infrared-II (NIR-II, 1000-1700 nm) fluorescence imaging can address these interferences. Combining NIR-II fluorescence imaging with PTT/PDT can significantly improve the accuracy of tumor theranostics and minimize damages to normal tissues. This review summarized recent advances in tumor PTT/PDT and NIR-II fluorophores, especially discussed achievements, challenges and prospects around NIR-II fluorescence imaging-guided PTT/PDT for cancers.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

Three Strategies in Engineering Nanomedicines for Tumor Microenvironment-Enabled Phototherapy

Canonical phototherapeutics have several limitations, including a lack of tumor selectivity, nondiscriminatory phototoxicity, and tumor hypoxia aggravation. The tumor microenvironment (TME) is characterized by hypoxia, acidic pH, and high levels of H2 O2 , GSH, and proteases. To overcome the shortcomings of canonical phototherapy and achieve optimal theranostic effects with minimal side effects, unique TME characteristics are employed in the development of phototherapeutic nanomedicines. In this review, the effectiveness of three strategies for developing advanced phototherapeutics based on various TME characteristics is examined. The first strategy involves targeted delivery of phototherapeutics to tumors with the assistance of TME-induced nanoparticle disassembly or surface modification. The second strategy involves near-infrared absorption increase-induced phototherapy activation triggered by TME factors. The third strategy involves enhancing therapeutic efficacy by ameliorating TME. The functionalities, working principles, and significance of the three strategies for various applications are highlighted. Finally, possible challenges and future perspectives for further development are discussed.

Recent advances in the role of endogenous hydrogen sulphide in cancer cells

Hydrogen sulphide (H2 S) is a gaseous neurotransmitter that can be self-synthesized by living organisms. With the deepening of research, the pathophysiological mechanisms of endogenous H2 S in cancer have been increasingly elucidated: (1) promote angiogenesis, (2) stimulate cell bioenergetics, (3) promote migration and proliferation thereby invasion, (4) inhibit apoptosis and (5) activate abnormal cell cycle. However, the increasing H2 S levels via exogenous sources show the opposite trend. This phenomenon can be explained by the bell-shaped pharmacological model of H2 S, that is, the production of endogenous (low concentration) H2 S promotes tumour growth while the exogenous (high concentration) H2 S inhibits tumour growth. Here, we review the impact of endogenous H2 S synthesis and metabolism on tumour progression, summarize the mechanism of action of H2 S in tumour growth, and discuss the possibility of H2 S as a potential target for tumour treatment.

Hydrogen Sulfide Responsive Phototherapy Agents: Design Strategies and Biological Applications

Hydrogen sulfide (H2S) is one of the critical gasotransmitters, which play important roles in regular physiological processes, especially in vital signaling pathways. However, fluctuations in endogenous H2S concentration can be linked to serious health problems, such as neurodegenerative diseases, cancer, diabetes, inflammation, cardiovascular diseases, and hypertension. Thus, it has attracted a great deal of attention in therapeutic applications, specifically in the field of phototherapy. Photodynamic therapy (PDT) and photothermal therapy (PTT) are two subclasses of phototherapy, which utilize either reactive oxygen species (ROS) or local temperature increase upon irradiation of a photosensitizer (PS) to realize the therapeutic action. Phototherapies offer unique advantages compared to conventional methods; thus, they are highly promising and popular. One of the design principles followed in new generation PSs is to build activity-based PSs, which stay inactive before getting activated by disease-associated stimuli. These activatable PSs dramatically improve the selectivity and efficacy of the therapy. In this review, we summarize small molecule and nanomaterial-based PDT and PTT agents that are activated selectively by H2S to initiate their cytotoxic effect. We incorporate single mode PDT and PTT agents along with synergistic and/or multimodal photosensitizers that can combine more than one therapeutic approach. Additionally, H2S-responsive theranostic agents, which offer therapy and imaging at the same time, are highlighted. Design approaches, working principles, and biological applications for each example are discussed in detail.

Quantitative 3D Temperature Rendering of Deep Tumors by a NIR-II Reversibly Responsive W-VO2@PEG Photoacoustic Nanothermometer to Promote Precise Cancer Photothermal Therapy

Accurately monitoring the three-dimensional (3D) temperature distribution of the tumor area in situ is a critical task that remains challenging in precision cancer photothermal (PT) therapy. Here, by ingeniously constructing a polyethylene glycol-coated tungsten-doped vanadium dioxide (W-VO2@PEG) photoacoustic (PA) nanothermometer (NThem) that linearly and reversibly responds to the thermal field near the human-body-temperature range, the authors propose a method to realize quantitative 3D temperature rendering of deep tumors to promote precise cancer PT therapy. The prepared NThems exhibit a mild phase transition from the monoclinic phase to the rutile phase when their temperature grows from 35 to 45 °C, with the optical absorption sharply increased ∼2-fold at 1064 nm in an approximately linear manner in the near-infrared-II (NIR-II) region, enabling W-VO2@PEG to be used as NThems for quantitative temperature monitoring of deep tumors with basepoint calibration, as well as diagnostic agents for PT therapy. Experimental results showed that the temperature measurement accuracy of the proposed method can reach 0.3 °C, with imaging depths up to 2 and 0.65 cm in tissue-mimicking phantoms and mouse tumor tissue, respectively. In addition, it was verified through PT therapy experiments in mice that the proposed method can achieve extremely high PT therapy efficiency by monitoring the temperature of the target area during PT therapy. This work provides a potential demonstration promoting precise cancer PT therapy through quantitative 3D temperature rendering of deep tumors by PA NThems with higher security and higher efficacy.

Molecular Engineering of pH-Responsive NIR Oxazine Assemblies for Evoking Tumor Ferroptosis via Triggering Lysosomal Dysfunction

Ferroptosis, a newly discovered form of regulated cell death, is emerging as a promising approach to tumor therapy. However, the spatiotemporal control of cell-intrinsic Fenton chemistry to modulate tumor ferroptosis remains challenging. Here, we report an oxazine-based activatable molecular assembly (PTO-Biotin Nps), which is capable of triggering the lysosomal dysfunction-mediated Fenton pathway with excellent spatiotemporal resolution via near-infrared (NIR) light to evoke ferroptosis. In this system, a pH-responsive NIR photothermal oxazine molecule was designed and functionalized with a tumor-targeting hydrophilic biotin-poly(ethylene glycol) (PEG) chain to engineer well-defined nanostructured assemblies within a single-molecular framework. PTO-Biotin Nps possesses a selective tropism to lysosome accumulation inside tumor cells, accommodated by its enhanced photothermal activity in the acidic microenvironment. Upon NIR light activation, PTO-Biotin Nps promoted lysosomal dysfunction and induced cytosolic acidification and impaired autophagy. More importantly, photoactivation-mediated lysosomal dysfunction via PTO-Biotin Nps was found to markedly enhance cellular Fenton reactions and evoke ferroptosis, thereby improving antitumor efficacy and mitigating systemic side effects. Overall, our study demonstrates that the molecular engineering approach of pH-responsive photothermal oxazine assemblies enables the spatiotemporal modulation of the intrinsic ferroptosis mechanism, offering a novel strategy for the development of metal-free Fenton inducers in antitumor therapy.

H2S Sensors: Synthesis, Optical Properties, and Selected Biomedical Applications under Visible and NIR Light

Hydrogen sulfide (H₂S) is an essential signaling gas within the cell, and its endogenous levels are correlated with various health diseases such as Alzheimer's disease, diabetes, Down's syndrome, and cardiovascular disease. Because it plays such diverse biological functions, being able to detect H₂S quickly and accurately in vivo is an area of heightened scientific interest. Using probes that fluoresce in the near-infrared (NIR) region is an effective and convenient method of detecting H₂S. This approach allows for compounds of high sensitivity and selectivity to be developed while minimizing cytotoxicity. Herein, we report a review on the synthesis, mechanisms, optical properties, and selected biomedical applications of H₂S sensors.

Tumor microenvironment-activated multi-functional nanodrug with size-enlargement for enhanced cancer phototheranostics

Phototheranostics that integrate diagnosis and treatment modalities have shown great promise in personalized cancer therapy. However, the "always on" characteristics often lead to suboptimal imaging quality and severe side effects. Herein, we report the construction of a perylenemonoimide based nanodrug CPMI NP with multi-functional activatable theranostic capability. The nanodrug is facilely co-assembled from a prodrug CPMI and DSPE-mPEG2000. In a tumor microenvironment (TME) with excessive glutathione (GSH), CPMI undergoes a cascade reaction to generate the phototheranostic molecule NPMI and the chemodrug chlorambucil, simultaneously switching on the near-infrared (NIR) fluorescence, photothermal effect, and drug release. The photothermal conversion efficiency is as high as 52.2%. Moreover, NPMI exhibits an enhanced intermolecular π-π stacking effect, leading to significant size-enlargement of the nanodrug and prolonged tumor retention. Due to TME-activation, the strong in vivo fluorescence signal of the tumor can be observed 144 h post injection with a high signal-to-noise ratio of up to 17. The enhanced tumor inhibition efficiency of the nanodrug is confirmed through activatable chemo-photothermal therapy. This work paves the way for the design of activatable phototheranostic agents for accurate cancer diagnosis and treatment.

Implications of hydrogen sulfide in colorectal cancer: Mechanistic insights and diagnostic and therapeutic strategies

Hydrogen sulfide (H₂S) is an important signaling molecule in colorectal cancer (CRC). It is produced in the colon by the catalytic synthesis of the colonocytes' enzymatic systems and the release of intestinal microbes, and is oxidatively metabolized in the colonocytes' mitochondria. Both endogenous H₂S in colonic epithelial cells and exogenous H₂S in intestinal lumen contribute to the onset and progression of CRC. The up-regulation of endogenous synthetases is thought to be the cause of the elevated H₂S levels in CRC cells. Different diagnostic probes and combination therapies, as well as tumor treatment approaches through H₂S modulation, have been developed in recent years and have become active area of investigation for the diagnosis and treatment of CRC. In this review, we focus on the specific mechanisms of H₂S production and oxidative metabolism as well as the function of H₂S in the occurrence, progression, diagnosis, and treatment of CRC. We also discuss the present challenges and provide insights into the future research of this burgeoning field.

Intelligent polymeric hydrogen sulfide delivery systems for therapeutic applications

Hydrogen sulfide (H₂S) plays an important role in regulating various pathological processes such as protecting mammalian cell from harmful injuries, promoting tissue regeneration, and regulating the process of various diseases caused by physiological disorders. Studies have revealed that the physiological effects of H₂S are highly associated with its concentrations. At relatively low concentration, H₂S shows beneficial functions. However, long-time and high-dose donation of H₂S would inhibit regular biological process, resulting in cell dysfunction and apoptosis. To regulate the dosage of H₂S delivery for precision medicine, H₂S delivery systems with intelligent characteristics were developed and a variety of biocompatibility polymers have been utilized to establish intelligent polymeric H₂S delivery systems, with the abilities to specifically target the lesions, smartly respond to pathological microenvironments, as well as real-timely monitor H₂S delivery and lesion conditions by incorporating imaging-capable moieties. In this review, we focus on the design, preparation, and therapeutic applications of intelligent polymeric H₂S delivery systems in cardiovascular therapy, inflammatory therapy, tissue regenerative therapy, cancer therapy and bacteria-associated therapy. Strategies for precise H₂S therapies especially imaging-guided H₂S theranostics are highlighted. Since H₂S donors with stimuli-responsive characters are vital components for establishing intelligent H₂S delivery systems, the development of H₂S donors is also briefly introduced.

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H₂S is an endogenous gasotransmitter that plays important role in regulating various physiological and pathological pathways.

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Controlled H₂S delivery is vital since the therapeutic effects of H₂S are highly associated with its concentrations.

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Intelligent polymeric H₂S delivery systems possess specific targeting, stimuli responsive and imaging guided capabilities, representing a strategic option for next generation of therapies.

Design strategies and applications of smart optical probes in the second near-infrared window

Over the last decade, a series of synergistic advances in the synthesis chemistries and imaging instruments have largely boosted a significant revolution, in which large-scale biomedical applications are now benefiting from optical bioimaging in the second near-infrared window (NIR-II, 1000-1700 nm). The large tissue penetration and limited autofluorescence associated with long-wavelength imaging improve translational potential of NIR-II imaging over common visible-light (400-650 nm) and NIR-I (750-900 nm) imaging, with ongoing profound effects on the studies of precision medicine. Unfortunately, the majority of NIR-II probes are designed as "always-on" luminescent imaging contrasts, continuously generating unspecific signals regardless of whether they reach pathological locations. Thus, in vivo imaging by traditional NIR-II probes usually suffers from weak detect precision due to high background noise. In this context, the advances of optical imaging now enter into an era of precise control of NIR-II photophysical kinetics. Developing NIR-II optical probes that can efficiently activate their luminescent signal in response to biological targets of interest and substantially suppress the background interferences have become a highly prospective research frontier. In this review, the merits and demerits of optical imaging probes from visible-light, NIR-I to NIR-II windows are carefully discussed along with the lens of stimuli-responsive photophysical kinetics. We then highlight the latest development in engineering methods for designing smart NIR-II optical probes. Finally, to appreciate such advances, challenges and prospect in rapidly growing study of smart NIR-II probes are addressed in this review.

Black graphitic carbon nitride nanosheets with mid-gap states realizing highly efficient near-infrared photo-thermal conversion for photoacoustic imaging

Developing metal-free photo-thermal transduction nanoagents (PTNAs) with high conversion efficiency addresses the balance between superior photothermal performance and good biocompatibility in the field of bio-applications of PTNAs. Herein, we highlight the bandgap-engineered black graphitic carbon nitride nanosheets (denoted as B-g-C₃N₄) as a novel metal-free PTNA with high conversion efficiency (62% at 808 nm) for photoacoustic imaging. The B-g-C₃N₄ absorbed infrared light with a narrowed bandgap and electronic states within the band (known as mid-gap states) due to the synergistic effect of sulfur incorporation, nitrogen vacancies and the porous structure. Notably, the mid-gap states mediated the non-irradiative recombination of electrons and holes, bringing about energy dissipated as phonons. Owing to the high conversion efficiency as well as superior biocompatibility, HeLa cells incubated with B-g-C₃N₄ can be ablated under 808 nm light illumination. Furthermore, the B-g-C₃N₄ realized cross-sectional multispectral optoacoustic tomography (MSOT) imaging of the U14-tumor-bearing mouse. This work expands the catalogue of highly efficient metal-free PTNAs, showing great promise in biological applications.

Metal-Organic Framework with Near-Infrared Luminescence for "Switch-on" Determination of Kaempferol and Quercetin by the Antenna Effect

The establishment of a reliable and sensitive method for the detection of flavonoids, such as kaempferol (Kae) and quercetin (Que), is important and challenging in food chemistry and pharmacology because numerous structural analogues may interfere with the detection. Until now, designing an efficient switch-on fluorescence sensing strategy for Kae and Que was still in the unachievable stage. In this work, a switch-on near-infrared (NIR) luminescence sensing assay for Kae and Que was fabricated based on a metal-organic framework (MOF) called IQBA-Yb for the first time. The fluorescence enhancing mechanism was that analytes served as additional "antenna" of Yb³⁺, leading to the efficient switch-on NIR emission under excitation at 467 nm. Meanwhile, the combination results of experiment and theoretical calculation revealed that there existed hydrogen bonds between Kae, Que, and the MOF skeleton, further promoting the energy transfer between the analyte and Yb³⁺ and facilitating fluorescence enhancement response. The developed probe possessed excellent sensing capability for Kae and Que, accompanied by a wide linear range (0.04-70, 0.06-90 μM), low detection limit (0.01, 0.06 μM), and short response time (20 min, 6 min), which was used to determine the Kae and Que contents in Green Lake and eatable Que samples with satisfactory results.

Hydrogen sulfide activatable metal-organic frameworks for Fluorescence Imaging-Guided Photodynamic Therapy of colorectal cancer

Photodynamic therapy (PDT) is a promising alternative and palliative therapeutic strategy for colorectal cancer (CRC). A novel photosensitizer with higher selectivity for CRC and fewer side effects is vital for clinical application. Given that the overexpression of hydrogen sulfide (H₂S) in CRC, it is expected to provide a selective stimulus for activatable photosensitizers that in respond to the specific microenvironment. Herein, we report a novel development of metal-organic frameworks (MOFs) composed of meso-Tetra (4-carboxyphenyl) porphine (TCPP) and ferric ion (Fe³⁺) through a facile one-pot process. Experiments both in vitro and in vivo reveal that the MOF is capable of depredating in response to the high content of H₂S in tumor microenvironment of CRC. Accompanying with the degradation and release of TCPP, the fluorescence and photosensitivity effect is switched from “off” to “on”, enabling the MOF to serve as a H₂S activatable nano-photosensitizer for real-time fluorescence imaging-guided and targeted PDT of CRC.

Tumor imaging and photothermal therapy in second near infrared window: A systematic review and meta-analysis

Background

Second near-infrared window (NIR-II, 1000-1700 nm) technology for tumor imaging and photothermal therapy (PTT) is an innovative method for tumor diagnosis and treatment. The NIR-II probe can specifically identify tumor cells, and effectively convert light energy into heat energy under the irradiation of NIR laser, thus achieving the integration of non-invasive tumor diagnosis and treatment. In the present study, we conducted a systematic review and meta-analysis of preclinical investigations to corroborate the efficacy and safety of photothermal therapy.

Methods

Relevant preclinical data were retrieved by searching PubMed, Web of Science, CNKI, WANFANG and VIP information databases. And the acquired data were analyzed by RevMan Version 5.3 software.

Results

According to the inclusion criteria, forty-two articles relating to NIR-II tumor imaging and PTT were recruited for further in-depth analysis. The NIR-II photoacoustic and fluorescence imaging could quickly and accurately identify tumor in mice, manifesting higher signal intensity on tumor site than that of normal tissue. After PTT, the tumor volume of mice decreased miraculously [RR=8.49, 95%CI (4.64, 15.55), P<0.00001], and even disappeared completely [RR=7.01, 95%CI (3.04, 16.13), P<0.00001] with no potential risk of affecting the blood routine.

Conclusions

PTT guided by NIR-II imaging can effectively diagnose the tumor lesion and eliminate it with the advantages of non-invasive and higher biosafety.

Activatable photothermal agents with target-initiated large spectral separation for highly effective reduction of side effects

Photothermal agents (PTAs) with minimized side effects are critical for transforming cancer photothermal therapy (PTT) into clinical applications. However, most currently available PTAs lack true selective activation to reduce side effects because of heavy spectral overlap between photothermal agents and their corresponding products. This study reports the construction of activatable PTAs with target-initiated large spectral separation for highly effective reduction of side effects. Such designed probes involve two H2O2-activatable PTAs, aza-BOD-B1 (single activatable site) and aza-BOD-B2 (multiple activatable site). After interacting with H2O2, aza-BOD-B1 only displays a mild absorption redshift (60 nm) from 750 nm to 810 nm with serious spectral overlap, resulting in a mild photothermal effect on normal tissues upon 808 nm light irradiation. In contrast, aza-BOD-B2 displays a large absorption spectral separation (150 nm) from 660 nm to 810 nm, achieving true selective activation to minimize side effects during PTT of cancer. Besides, in vitro and in vivo investigations demonstrated that aza-BOD-B2 can specifically induce photothermal ablation of cancer cells and tumors while leaving normal sites undamaged, whereas aza-BOD-B1 exhibits undesirable side effects on normal cells. Our study provides a practical solution to the problem of undesired side effects of phototherapy, an advance in precision medicine.

Nano-assemblies from J-aggregated dyes to improve the selectivity of a H2S-activatable photosensitizer

We report J-aggregates of a boron dipyrromethene derivative (BDP-Nit) as an H₂S-activatable nano-photosensitizer. The closely packed BDP-Nit in J-aggregates exhibits high selectivity to H₂S over biothiols to produce an active photosensitizer.

Iodine-Rich Nanoadjuvants for CT Imaging-Guided Photodynamic Immunotherapy of Breast Cancer

Immunotherapy, which stimulates the body's own immune system to kill cancer cells, has shown great promise in the field of cancer therapy. However, the uncontrolled biodistribution of immunotherapeutic drugs may cause severe side effects. Herein, we report an iodine-rich nanoadjuvant (INA) for photo-immunotherapy. INA is prepared by encapsulating a toll-like receptor 7 agonist (R837) and a photosensitizer (phthalocyanine) into an iodine-rich amphiphilic copolymer PEG-PHEMA-I. By virtue of the enhanced permeation and retention (EPR) effect, INA can effectively accumulate into the tumor site. Under light irradiation, photodynamic therapy (PDT) triggered by INA will induce immunogenic cell death (ICD) in the tumor region to trigger the release of immune-associated cytokines. Such a process may further induce the maturation of dendritic cells which will be accelerated by R837, leading to the proliferation of effector T cells for immunotherapy. The photo-immunotherapy mediated by INA shows good anticancer efficacy both in vitro and in vivo. Meanwhile, INA is also a CT contrast agent owing to its high density of iodine, which can successfully illuminate tumors by CT imaging. Thus, our study develops a light-triggered nanoadjuvant for CT imaging-guided enhanced photo-immunotherapy.

Recent Advances in Near-Infrared-II Fluorescence Imaging for Deep-Tissue Molecular Analysis and Cancer Diagnosis

Fluorescence imaging with high sensitivity and minimal invasiveness has received tremendous attention, which can accomplish visualized monitoring and evaluation of cancer progression. Compared with the conventional first near-infrared (NIR-I) optical window (650-950 nm), fluorescence imaging in the second NIR optical window (NIR-II, 950-1700 nm) exhibits deeper tissue penetration capability and higher temporal-spatial resolution with lower background interference for achieving deep-tissue in vivo imaging and real-time monitoring of cancer development. Encouraged by the significant preponderances, a variety of multifunctional NIR-II fluorophores have been designed and fabricated for sensitively imaging biomarkers in vivo and visualizing the treatment procedure of cancers. In this review, the differences between NIR-I and NIR-II fluorescence imaging are briefly introduced, especially the advantages of NIR-II fluorescence imaging for the real-time visualization of tumors in vivo and cancer diagnosis. An important focus is to summarize the NIR-II fluorescence imaging for deep-tissue biomarker analysis in vivo and tumor tissue visualization, and a brief introduction of NIR-II fluorescence imaging-guided cancer therapy is also presented. Finally, the significant challenges and reasonable prospects of NIR-II fluorescence imaging for cancer diagnosis in clinical applications are outlined.

Log P analyzation-based discovery of GSH activated biotin-tagged fluorescence probe for selective colorectal cancer imaging

Targeted activatable fluorescent probes could provide an effective approach for colorectal cancer imaging. In this study, F1 was found as an effective targeted activatable fluorescent probe based on log P analysis. In vitro experiments demonstrated that the initial fluorescence of the developed probe F1 was initially well quenched, and the fluorescence increased after the probe interacted with glutathione. Cell imaging results showed that the probe had good cell permeability and selectivity. Remarkably, F1 displayed enhanced tumor tissue fluorescence in MC-38 tumor-bearing mice. Notably, it showed selectivity in imaging clinical specimens of human colorectal cancer tissues. Accordingly, this study shows that log P analysis can facilitate the developing efficient of biotin-tagged activatable probes, and the identified F1 has a good potential in clinical colorectal cancer diagnosis.

Tumor microenvironment-responsive versatile "Trojan horse" theranostic nanoplatform for magnetic resonance imaging-guided multimodal synergistic antitumor treatment

A natural killer (NK)-92 cell membrane-camouflaged mesoporous MnO₂-enveloped Au@Pd (Au@Pd@MnO₂) nanoparticles (denoted as APMN NPs)-based versatile biomimetic theranostic nanoplatform was developed for magnetic resonance (MR) imaging-guided multimodal synergistic antitumor treatments. In this core-shell nanostructure, an Au@Pd core induced near-infrared (NIR)-activatable hyperthermal effects and nanozyme catalytic activity, while a mesoporous MnO₂ shell not only afforded a high drug-loading capability, tumor microenvironment (TME)-triggered MR imaging and drug release, but also endowed catalase-, glutathione peroxidase-, and Fenton-like activities. Furthermore, the NK-92 cell membrane camouflaging endowed the NPs with enhanced tumor-targeting capability, immune escape function, and membrane protein-mediated tumoral uptake property. The doxorubicin-loaded APMN (D-APMN) NPs exhibited TME-responsive drug release properties. Furthermore, the cellular uptake, in vivo MR imaging, and NIR thermal imaging confirmed the active tumor-targeting capability and TME-responsive MR imaging property of these biomimetic NPs. An antitumor efficacy test, histological analyses, and blood biochemical profiles suggested that the developed D-APMN NPs possessed a high antitumor activity and biosafety in tumor-bearing nude mice. Therefore, the developed APMN NPs held great potential as an intelligent and comprehensive theranostic nanoplatform for tumor-specific bioimaging and TME-responsive multimodality treatment based on photothermal therapy, chemodynamic therapy, and chemotherapy. STATEMENT OF SIGNIFICANCE: Exploring intelligent and comprehensive theranostic nanoplatforms to integrate tumor-specific bioimaging and TME-responsive multimodal therapy effectively is a challenge. Herein, we successfully developed a new kind of NK-92 cell membrane-camouflaged mesoporous MnO₂-enveloped Au@Pd nanoparticles (APMN NPs)-based versatile biomimetic theranostic nanoplatform for the potential MR imaging-guided multimodal synergistic antitumor treatments. These NPs could integrate unique structural, optical, multiple-catalytic, paramagnetic, and biological merits of NK-92 cell membrane, Au@Pd cores and mesoporous MnO₂ shell in a single nanoplatform. The NK-92 cell membrane camouflaging endowed the NPs with enhanced tumor-targeting capability, immune escape function, and membrane protein-mediated tumoral uptake property. The new information obtained from this study may be beneficial to promote the development of novel TME-responsive versatile "Trojan horse" theranostic nanoplatforms for efficient MR imaging-guided multimodal synergistic treatment.

Smart nanomaterials for cancer diagnosis and treatment

Innovations in nanomedicine has guided the improved outcomes for cancer diagnosis and therapy. However, frequent use of nanomaterials remains challenging due to specific limitations like non-targeted distribution causing low signal-to-noise ratio for diagnostics, complex fabrication, reduced-biocompatibility, decreased photostability, and systemic toxicity of nanomaterials within the body. Thus, better nanomaterial-systems with controlled physicochemical and biological properties, form the need of the hour. In this context, smart nanomaterials serve as promising solution, as they can be activated under specific exogenous or endogenous stimuli such as pH, temperature, enzymes, or a particular biological molecule. The properties of smart nanomaterials make them ideal candidates for various applications like biosensors, controlled drug release, and treatment of various diseases. Recently, smart nanomaterial-based cancer theranostic approaches have been developed, and they are displaying better selectivity and sensitivity with reduced side-effects in comparison to conventional methods. In cancer therapy, the smart nanomaterials-system only activates in response to tumor microenvironment (TME) and remains in deactivated state in normal cells, which further reduces the side-effects and systemic toxicities. Thus, the present review aims to describe the stimulus-based classification of smart nanomaterials, tumor microenvironment-responsive behaviour, and their up-to-date applications in cancer theranostics. Besides, present review addresses the development of various smart nanomaterials and their advantages for diagnosing and treating cancer. Here, we also discuss about the drug targeting and sustained drug release from nanocarriers, and different types of nanomaterials which have been engineered for this intent. Additionally, the present challenges and prospects of nanomaterials in effective cancer diagnosis and therapeutics have been discussed.

NIRII-HDs: A Versatile Platform for Developing Activatable NIR-II Fluorogenic Probes for Reliable In Vivo Analyte Sensing

Small-molecule-based second near-infrared (NIR-II) activatable fluorescent probes can potentially provide a high target-to-background ratio and deep tissue penetration. However, most of the reported NIR-II activatable small-molecule probes exhibit poor versatility owing to the lack of a general and stable optically tunable group. In this study, we designed NIRII-HDs, a novel dye scaffold optimized for NIR-II probe development. In particular, dye NIRII-HD5 showed the best optical properties such as proper pK_a value, excellent stability, and high NIR-II brightness, which can be beneficial for in vivo imaging with high contrast. To demonstrate the applicability of the NIRII-HD5 dye, we designed three target-activatable NIR-II probes for ROS, thiols, and enzymes. Using these novel probes, we not only realized reliable NIR-II imaging of different diseases in mouse models but also evaluated the redox potential of liver tissue during a liver injury in vivo with high fidelity.

Recent Progress of Cyanine Fluorophores for NIR-II Sensing and Imaging

The cyanine fluorophores, a kind of classic organic fluorophores, are famous for their high extinction coefficient, simple synthetic route, and relatively long absorption and emission wavelengths. Moreover, the excellent biocompatibility and low toxicity in biological samples make cyanine fluorophores show excellent application value in the biomedical field, especially in Near-Infrared II (NIR-II) sensing and imaging. In this review, we briefly outline the history, characteristics, and current state of development of cyanine fluorophores. In particular, we described the application of cyanine fluorophores in NIR-II sensing and imaging. We hope this review can help researchers grab the latest information in the fast-growing field of cyanine fluorophores for NIR-II sensing and imaging.

Simultaneous Enhancement of the Long-Wavelength NIR-II Brightness and Photothermal Performance of Semiconducting Polymer Nanoparticles

Theranostic agents with fluorescence in the second near-infrared (NIR-II) window, especially in its long-wavelength region, and NIR-II-excitable photothermal effect is promising but challenging in tumor diagnosis and therapy. Here, we report a simple but effective strategy to develop semiconducting polymer nanoparticles-based theranostic agents (PBQx NPs) and demonstrate their applications for long-wavelength NIR-II fluorescence imaging beyond 1400 nm and photothermal therapy (PTT) of tumors upon excitation at 1064 nm. Both experimental results and theory calculations show that the brightness and photothermal performance of PBQx NPs can be simultaneously improved by simply increasing the repeating unit number of semiconducting polymers. For example, PBQ45 NPs have 5-fold higher brightness than PBQ5 NPs and 6.7-fold higher photothermal effect (based on PCE × ε) than PBQ3 NPs, and exhibit promising applications in long-wavelength NIR-II fluorescence abdomen imaging, image-guided tumor resection, and image-guided PTT. This study demonstrates the effectiveness and importance of repeating unit numbers in regulating the theranostic performance, which has not received enough attention before.

Stable twisted conformation aza-BODIPY NIR-II fluorescent nanoparticles with ultra-large Stokes shift for imaging-guided phototherapy

Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) holds great promise for in vivo imaging and imaging-guided phototherapy with deep penetration and high spatiotemporal resolution. It is very appealing to obtain NIR-II fluorescent probes through simple procedures and economical substrates. Herein, we developed a D-A-D' structure NIR-II photosensitizer (triphenylamine modified aza-Bodipy, TAB) based on the strong electron-withdrawing nature of borane difluoride azadipyrromethene's center (aza-BODIPY). Subsequently, halogen atoms (Br, I) were introduced to the TAB molecule, and TAB-2Br and TAB-2I were synthesized. Compared to the TAB molecule, a significant redshift in the emission wavelength, ultra-large Stokes shift (>300 nm), and enhanced singlet oxygen production capacity were acquired for the halogenated molecules. After self-assembly of TABs and an amphiphilic polypeptide POEGMA₂₃-PAsp₂₀, the obtained P-TAB, P-TAB-2Br, and P-TAB-2I nanoparticles exhibited excellent water solubility and biocompatibility, remarkable photothermal conversion efficiency (beyond 40%), and good resistance to photobleaching, heat, and H₂O₂. Under 808 nm laser irradiation, the P-TAB-2I exhibited an efficient photothermal effect and ROS generation in vitro. And in vivo experiments revealed that P-TAB-2I displayed efficient NIR-II fluorescence imaging and remarkable tumor ablation results. All of these results make TAB-2I potential organic probes for clinical NIR-II fluorescence imaging and cancer phototherapy.

A turn-on NIR fluorescence sensor for gossypol based on Yb-based metal-organic framework

The development of analytical method for selective and sensitive detection of gossypol (Gsp), an extraction from the cotton plants, is important but still challenging in food safety and medical field. Herein, we reported a turn-on near infrared (NIR) fluorescence detection strategy for Gsp based on a metal-organic framework (MOF), QBA-Yb, which was prepared from 4,4'-(quinolone-5, 8-diyl) benzoate with Yb(NO₃)₃·5H₂O by solvothermal synthesis. The Gsp acted as another "antenna" to sensitize the luminescence of Yb³⁺, leading to the turn-on NIR emission upon 467 nm excitation. As Gsp concentration increased, the NIR emission at 973 nm enhanced gradually, thus enabling highly sensitive Gsp detection in a turn-on way. The experiment and theoretical calculation results revealed the presence of strong hydrogen bonds between Gsp molecules and the MOF skeleton. The developed QBA-Yb probe showed excellent characteristics for detection of Gsp molecules, accompanied by wide linear range (5-160 μg/mL), low detection limit (0.65 μg/mL) and short response time (within 10 min). We have further demonstrated that the QBA-Yb probe was successfully applied for the determination of Gsp in real samples of cottonseeds.

Engineering of an endogenous hydrogen sulfide responsive smart agent for photoacoustic imaging-guided combination of photothermal therapy and chemotherapy for colon cancer

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Engineering of a endogenous hydrogen sulfide responsive combination of photothermal therapy and chemotherapy for colon cancer.

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HKUST-1 was loaded with curcumin as an endogenous hydrogen sulfide-triggered smart agent.

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Cur@HKUST-1@PVP allows selective colon cancer tumor imaging.

Introduction

Photothermal therapy can be synergistically combined with chemotherapy to improve the therapeutic effect for colon cancer. However, conventional therapeutic agents have side effects in normal tissues, limiting their application.

Objectives

To reduce these side effects, a smart agent (Cur@HKUST-1@PVP) whose functionality is triggered by the high content of endogenous hydrogen sulfide in colon tumors was engineered for photoacoustic imaging-guided combination of photothermal therapy and chemotherapy for colon tumors.

Methods

After reacting with hydrogen sulfide, Cur@HKUST-1@PVP simultaneously generates CuS and releases curcumin. The generated CuS serves as an imaging agent for both photothermal therapy and photoacoustic imaging, while the released curcumin is used for chemotherapy.

Results

In vivo photoacoustic imaging experiments demonstrated that Cur@HKUST-1@PVP can be used for selectively imaging colon cancer tumors. In vivo experiments in mice for treatment suggested that the endogenous hydrogen sulfide-activated combination of photothermal therapy and chemotherapy has a better treatment effect that photothermal therapy or chemotherapy treatment alone.

Conclusion

The endogenous hydrogen sulfide-activated Cur@HKUST-1@PVP agent developed herein shows great potential for the accurate diagnosis and effective treatment of colon cancer.

Hydrogen Sulfide: An Emerging Precision Strategy for Gas Therapy

Advances in nanotechnology have enabled the rapid development of stimuli-responsive therapeutic nanomaterials for precision gas therapy. Hydrogen sulfide (H₂ S) is a significant gaseous signaling molecule with intrinsic biochemical properties, which exerts its various physiological effects under both normal and pathological conditions. Various nanomaterials with H₂ S-responsive properties, as new-generation therapeutic agents, are explored to guide therapeutic behaviors in biological milieu. The cross disciplinary of H₂ S is an emerging scientific hotspot that studies the chemical properties, biological mechanisms, and therapeutic effects of H₂ S. This review summarizes the state-of-art research on H₂ S-related nanomedicines. In particular, recent advances in H₂ S therapeutics for cancer, such as H₂ S-mediated gas therapy and H₂ S-related synergistic therapies (combined with chemotherapy, photodynamic therapy, photothermal therapy, and chemodynamic therapy) are highlighted. Versatile imaging techniques for real-time monitoring H₂ S during biological diagnosis are reviewed. Finally, the biosafety issues, current challenges, and potential possibilities in the evolution of H₂ S-based therapy that facilitate clinical translation to patients are discussed.

Supramolecular J-aggregates of aza-BODIPY by Steric and π-π Interactions for NIR-II Phototheranostic

Achieving J-aggregation of a molecule is a fascinating way to construct fluorescent imaging as well as photothermal therapy agents in the second near-infrared window. Modulation of the balance between intermolecular...

Near-Infrared-II Bioimaging for in Vivo Quantitative Analysis

Near-Infrared-II (NIR-II) bioimaging is a newly emerging visualization modality in real-time investigations of biological processes research. Owning to advances in reducing photon scattering and low tissue autofluorescence levels in NIR-II region (1,000-1700 nm), NIR-II bioimaging affords high resolution with increasing tissue penetration depth, and it shows greater application potential for in vivo detection to obtain more detailed qualitative and quantitative parameters. Herein, this review summarizes recent progresses made on NIR-II bioimaging for quantitative analysis. These emergences of various NIR-II fluorescence, photoacoustic (PA), luminescence lifetime imaging probes and their quantitative analysis applications are comprehensively discussed, and perspectives on potential challenges facing in this direction are also raised.